Fix rootfs size writing

src/scripts/mod_for_test_scripts/000recordRootFsSize

Index: src/scripts/mod_for_test_scripts/000recordRootFsSize
diff --git a/src/scripts/mod_for_test_scripts/000recordRootFsSize b/src/scripts/mod_for_test_scripts/000recordRootFsSize
index 7ba224c5a85fe3e11ba271983f6a577e4f1b3dda..3540b82cc499e18a4bba6f3b0727cadf2bb0821d 100755
--- a/src/scripts/mod_for_test_scripts/000recordRootFsSize
+++ b/src/scripts/mod_for_test_scripts/000recordRootFsSize
@@ -13,7 +13,10 @@ echo "Recording production image size."
 FILE="${ROOT_FS_DIR}/root/bytes-rootfs-prod"
 if [[ ! -f "${FILE}"  ]]; then
   # This will complain it cannot find a valid mtab so keep it quiet.
-  df -B1 -P 2>/dev/null | grep ${ROOT_FS_DIR} | awk '{ print $3 }' > "${FILE}"
+  # Grep for rootfs mount at end of line otherwise we will get rootfs/var
+  # mount point as well.
+  df -B1 -P 2>/dev/null | grep "${ROOT_FS_DIR}$" | awk '{ print $3 }' > \
+      "${FILE}"
 else
   echo "  Not modifying existing ${FILE}."
 fi